Most of the callers were students. Some were professors or faculty members. All were in a state of disbelief.

Audio files of the eight calls paint a picture of an incredulous, nervous situation at the MSU Engineering Building as the event unfolded about 1 p.m. One student caller described an older man with a white beard screaming profanities and pacing naked through the hallway.

Another caller, a professor who was in a nearby classroom at the time, relayed the panic setting in as some feared McCarthy was armed.

"I don't know his name, but he's shouting that 'I've got a gun' or something, so we all moved out of the building," the professor tells a dispatcher. "He's still walking the hallway."

Dispatchers received the first call on the incident just before 1:04 p.m. MLive Media Group obtained audio files of each emergency call from Ingham County Central Dispatch through a Freedom of Information Act request.

"He's yelling, 'I have a gun' and he's rambling something we don't understand, but he's completely naked and he's walking the hallway," the professor says.

MSU math professor John McCarthy (Photo courtesy MSU)

McCarthy, 57, reportedly shouted about Steve Jobs, God, religion and other topics during his Calculus I class, then stripped naked and continued screaming in the Engineering Building's hallway. He was not armed.

Witnesses took to social media, posting numerous firsthand accounts of the incident around the Internet, launching the incident into national headlines. One witness posted to Reddit a picture of a naked McCarthy, handcuffed and sitting on the Engineering Building floor.

MSU police placed McCarthy in protected custody and transported him to a local hospital. He will not be charged with a crime, according to police. The professor who called 911 may have misheard McCarthy as he shouted. Several witness accounts suggest McCarthy screamed, "There is no God."

"There is an irate individual in the hallway of the Engineering Building at MSU and he is walking up and down the hallway screaming at the top of his lungs and swearing profusely," one student reported in a 911 call. "He's disrupting all the classes."

The responding dispatcher asked the student if he knew what prompted McCarthy's outburst.

"No, he was [inaudible] religion for a minute and something wrong," the caller said. "We have no idea what he was screaming about."

"The incident that occurred Monday was unfortunate," he writes. "Although I do not remember what happened, I have been told that I may have caused distress among my students during Monday's class. For this I am truly sorry.

"Your education and well-being is and always has been my number one priority," McCarthy continues in the message. "So at this point it seems best that another instructor take over this class for the remainder of the semester."

MSU has not taken personnel action against McCarthy. The matter will be addressed at a later date, according to a university spokesperson.

Dispatchers forwarded information on the disturbance to MSU police at 1:07 p.m., according to the university. Officers arrived at the scene by 1:11 p.m. and had detained McCarthy by 1:15 p.m.

Listen to all eight emergency calls below. Some have been edited to redact callers' personal information.